Diesel Engine Cold-Start with Ignition-Assist Device
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Solution Overview
Problem
Diesel engines face challenges in starting in cold environments due to the high autoignition temperature of low-cetane fuels, which requires higher thermal energy for ignition, and the difficulty in achieving autoignition in cold conditions.
Innovation Solution
The use of an ignition-assist device such as a glow plug, spark plug, or plasma ignition device during cold-start until the engine reaches a temperature at which autoignition occurs, combined with strategies like preheating the intake air and using a thermal barrier coating to retain thermal energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If low-cetane fuel is used to reduce emissions and improve fuel flexibility, then adaptability is improved, but cold-start capability deteriorates due to higher autoignition temperature requirements
Solution Approach 1:
The system performs preliminary heating actions before the main combustion event. A glow plug or spark plug is activated beforehand to preheat the combustion chamber or ignite the fuel, enabling cold-start operation with low-cetane fuels that would otherwise be too difficult to ignite in cold conditions
Solution Approach 2:
An intermediary ignition device (glow plug or spark plug) is introduced to mediate between the low-cetane fuel and the combustion process. This intermediary provides the initial thermal energy or spark needed to start combustion, allowing the low-cetane fuel to burn reliably in cold conditions without requiring high-cetane properties
2Reliability
If thermal assistance is provided during cold-start to enable ignition, then cold-start capability is improved, but energy consumption increases due to additional heating requirements
Solution Approach 1:
The ignition assist device is activated only during the cold-start period as a preliminary action, then deactivated once the engine reaches operating temperature. This temporary preliminary heating provides the necessary cold-start capability while limiting energy consumption to only when absolutely necessary
Solution Approach 2:
The ignition assist device operates periodically or intermittently during cold-start rather than continuously. It is activated in pulses or for specific durations needed to establish combustion, then turned off, creating a periodic action pattern that reduces overall energy consumption compared to continuous operation
3Use of energy by moving object
If compression ratio is increased to improve thermal efficiency and enable autoignition, then energy efficiency is improved, but device complexity increases due to stricter manufacturing tolerances
Solution Approach 1:
The system changes the ignition mechanism parameter from relying solely on compression-heating to using an active ignition source (spark plug or glow plug). This parameter change allows the use of lower compression ratios with wider tolerances while maintaining thermal efficiency, as the ignition is initiated by the plug rather than purely by compression temperature
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables successful cold-starting of CI engines with low-cetane fuels by providing the necessary thermal assistance for ignition, reducing the time to reach stable idle speeds, and minimizing pollutant emissions during the cold-start period.
Implementation Method 1
an ignition-assist device such as a glow plug, a spark plug, or a plasma ignition device can be used during cold-start until the engine reaches a temperature at which autoignition occurs
Implementation Method 2
using a thermal barrier coating to retain thermal energy
Implementation Method 3
moving the piston from a bottom-dead-center (BDC) position to a top-dead-center (TDC) position in the combustion chamber at a compression ratio of between about 15 and about 25
Data Source
AI summary
Embodiments described herein relate to systems and methods of operating internal combustion (IC) engines by combusting various fuel chemistries therein. Specifically, engines described herein can operate a wide range of fuel chemistries with varying molecular formulas. The chemical compositions of the fuels described herein make them more difficult to ignite than long chain hydrocarbons (i.e., fuels that include 6 or more carbon atoms in a molecule). In some embodiments, engines described herein can combust fuels that have the chemical properties of alcohols. In some embodiments, engines described herein can combust fuels that include hydroxide groups. Examples of such fuels include methanol and/or ethanol. In some embodiments, engines described herein can combust natural gas. These fuel chemistries are difficult to ignite, particularly at low temperatures and during initial engine startup. Systems and methods described herein address these ignition difficulties, particularly in diesel engine architectures.